1. Field of Invention
The invention relates to medical instruments and more particularly to a disposable, safe medical syringe with a retractable needle.
2. Description of Related Art
Special attention should be given to syringe needles because they are sharp enough to cause needle stick injuries before and after use. In particular, if a user is accidentally injured by a blood-stained needle, serious infections might be caused through the needle. Hence, safe medical syringes with retractable needles have been invented and some are commercially available.
For example, U.S. Pat. No. 7,276,049 discloses a disposable safety syringe designed to prevent syringe handlers from being pricked by a needle by covering the needle with a needle shield. The needle is covered with the needle shield after use. The needle shield is fitted over a syringe cylinder. A stopping tab prevents the needle shield from sliding off the cylinder. Inserting tabs are formed by cutting part of shield walls, and locking grooves are formed in the end of the inserting tabs. A fixing adapter has an engagement member formed in the inner side thereof and a number of elastic fins in the outer side thereof, which is fitted on the locking tab of the needle fixer.
Further, U.S. Pat. No. 7,393,340 discloses a disposable safety syringe including an automatically retractable needle. The syringe includes an automatically retractable needle for preventing said syringe from being reused, a cylindrical body defining, at one end thereof, a needle coupling end-piece and being opened at the other end portion thereof for introducing thereinto a piston having a scaling gasket. The patent is characterized in that on the piston are provided engaging means for engaging and retracting the needle after the delivering of the injection liquid.
Furthermore, U.S. Pat. No. 7,410,478 discloses a safety syringe with a needle retracting mechanism. The safety syringe includes a flexible holder-supporting seat that is sleeved around and that clamps a needle holder within a front end portion of a syringe barrel. A flexible sealing member seals an open front end of a plunger so as to define a vacuuming chamber in the plunger. When the plunger moves within the barrel to a front limit position, a holder-retaining front portion of the sealing member engages and retains the needle holder thereon. The plunger pushes the holder-supporting seat to separate from the needle holder such that the sealing member and the needle holder mover rearward within the syringe barrel due to negative pressure produced in the plunger, thereby retracting a needle into the syringe barrel.
Thus, the need for improvement still exists.